Contemporary evaporative emission control systems typically comprise a solenoid-operated purge valve that is under the control of a purge control signal generated by a microprocessor-based engine management system. A typical purge control signal is a duty-cycle modulated pulse waveform having a relatively low frequency, for example in the 5 Hz to 50 Hz range. The modulation may range from 0% to 100%. The reciprocation response of the armature of certain known solenoid-operated purge valves may be sufficiently fast that the armature closely follows the pulse waveform input, especially at lower waveform frequencies. Such pulsating reciprocation may at times produce audible noise that may be deemed objectionable. The noise may even be viewed by the vehicle owner as a potential defect that requires the source of noise to be checked out by a competent service facility, even though the valve is actually operating properly. Such noise may be aggravated at low temperatures in the case of a valve that has an elastomeric seal because such seals typically become stiffer as temperature drops.
Commonly owned U.S. Pat. No. 4,901,974 issued 20 Feb. 1990 shows a canister purge solenoid valve that axially reciprocates in response to a pulsating electrical input. That valve has a sealing means on the end of the armature forming the valve head. This sealing means is designed to impact the seat upon valve closure and also to impact a fixed stop upon the armature coming to its maximum displacement away from the seat (i.e., maximum valve opening). The end of the stator that confronts the end of the armature opposite the armature's head end contains a resilient bumper that is impacted by the armature as the armature comes to its maximum displacement away from the seat so that the armature's impact is shared by both the bumper and a portion of the sealing means as the armature comes to its maximum opening.
A general objective of the present invention is to attenuate audible noise of a purge valve sufficiently that it will be eliminated, or at least attenuated to a level that should not be deemed objectionable, thereby reducing the likelihood that a properly function might be considered to have a noise-producing problem that should be investigated. Moreover, the invention accomplishes this noise-attenuation objective without sacrificing valve performance, and the invention further provides improved sealing of the flow path through the valve when the valve is closed. In exemplary embodiments to be herein disclosed, the portion of the armature that forms the valve head is provided with a novel one-piece seal element having at one axial end that is toward the valve seat, a frustoconically tapered bead forming a seal that flexes slightly as it closes on the valve seat, wiping slightly across the seat as it comes to full closure against the seat surface. In one of the exemplary embodiments, the opposite axial end of the seal element comprises an annular axial wall whose free end comes into abutment with the free end of a confronting annular axial wall fixedly disposed on the valve body as the armature comes to its maximum displacement away from the seat. In another of the exemplary embodiments, a damper is disposed between the axial end of the armature that is opposite the head end, and this damper absorbs impact between the armature and a pole piece of a solenoid's stator as the armature comes to its maximum displacement away from the seat.
The foregoing, along with additional features, and other advantages and benefits of the invention, will be seen in the ensuing description and claims which are accompanied by drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at this time for carrying out the invention.